Furoquinoxalines and thienoquinoxalines as catalysts in dye bleach baths for color photography



Patented Feb. 16, 1 954 FUROQUINOXALINES AND THIENOQUINOX- ALINES AS CATALYSTS IN DYE BLEACH BATHS FOR COLOR PHOTOGRAPHY Fritz W. H. Mueller, Binghamton, N. Y., assignor to General Aniline & Film Corporation, New York, N. Y., a corporation of Delaware No Drawing. Application December 10, 1952,

Serial No. 325,218

16 Claims. (Cl. 95-88) This invention relates to a method of processing photographic color pictures and more particularly to the use of furoquinoxalines and thienoquinoxalines as accelerators for dye bleach baths employed in producing dyestufi images from dyed silver images.

It is known that the silver dye bleach-out process involves the treatment of difiusely dyed silver halide emulsions with a bleaching solution which, in cooperation with a silver image, destroys the dye at the places of said image thereby yielding dyestuif images. The dyes which are employed in the diifuse dyeing of the silver halide emulsion layers are primarily azo dyes or the substantive and acid type, although some basic vat dyes and alizarines may also be employed.

The silver azo dye bleach-out process operates on the principle that the metallic silver image in cooperation with the various reagents in the bleach composition functions as the reducing agent for the azo linkage, thereby efiecting the reduction of the azo dye in situ with the silver image. In other Words, the bleaching or decolorization of the dyestuiTs is accomplished in a bleach bath in which there occurs a simultaneous decolorization of the dye with oxidation of the metal image at the point where silver is present. The metallic silver is thereby converted into a silver compound which may be subsequently removed by fixation in a hypo-solution or in a solution of another silver halide solvent such as ammonium thiocyanate or a water soluble iodide such as potassium iodide and the like.

The bleach bath usually employed in this process contains an aqueous solution of a mineral acid or a mineral acid containing an alkali metal or ammonium halide such as potassium bromide, potassium chloride, potassium iodide or the cor.- responding sodium or ammonium salts. Such baths require a relatively long treating time to ensure destruction of the dyestufis present in situ with the silver image. Long treatments in a bleaching solution of high acidity have the tendency to soften the gelatin of the photographic emulsion containing the silver image and bleachable dye. I It has, accordingly, been proposed to employ various organic compounds as catalysts to accelerate the action of such bleach baths and thereby materially reduce the bleaching time.

The most practical catalysts suggested so far are the azines such as phenazine, 2,3-diamino phenazine and the like. Although phenazine and its substituted derivatives are eiiective as accelerators, they are highly colored substances and substantive to gelatin. Consequently, they leave a stain in the gelatin layer which is difiicult to remove and which seriously afiects the quality of the final image. r

This feature is particularly undesirable when dye masks, prepared in a tripack or multilayer film containing dye images of the azomethine or quinonimine type are employed. Then, the baths containing mineral acids of high concentrations, can no longer be tolerated because they tend to destroy the color developed azomethine or quinonimine dye images.

I have discovered that furoquinoxalines and thienoquinoxalines are highly eiTective catalysts for silved dye bleach baths, that they are not 'substantive to gelatin, do not stain the gelatin layer and do not affect the quality of the final image and the employment of such compounds in this relationship constitutes the purposes and Objects of my invention. 1 l 4 The furoquinoxalines and thienoquinoxalines contemplated herein are characterized by the following general formula:

naphthene series such as benzo, naphtho, anthro,

acenaphtho; alkoxybenzo, e. g., methoxybenzo, ethoxybenzo, etc.; lower alkylbenzo, e. g., methylbenzo, ethylbenzo, etc.; halogen substituted benzo,

e. g., chlorobenzo, bromoben zo and the like.

The following are illustrative of furoquinoxalines and thienoquinoxalines which have been employed for my purpose.

Beuzofuro[2,3-b]quinoxa1ine Coumarophenazine) Q-methylbenzo furo [2,3-b1quinoxaliue I 8-metlzylbenzofuro [23-h] qui nox aline CH Naphtho [1 ',2',4,5] thieno [2,3-b1acenaphtheno -e] pyrazine Naphtho[2',1,4,5lthieno [2,3-b1quinoxaline (a-naphthothiofurazine) S H, U m

9-chloro-10-methylnaphthc[2,1,4,5] thieno [2,3-b] quinoxaline Q-ethoxynaphtho [2 ',1 ',4,5 thieno [2,3-b] quinoxaline I H: CH N N aphtho [2',1',4,5] thieno [2, 3b] acenaphtheno[4,5-e] pyrazme The foregoing furoquinoxalines are prepared by the condensation of an o-phenylene diamine or its homologues with a 2,3-diketocoumaron or its homologues according to the method described in Berichte vol. 34, p. 1110.

The foregoing thienoquinoxalines are prepared by the reaction of an o-phenylene diamine or its homologues with a 2,3-diketodihydro benzethiophene or naphthothiophene according to the method described in Berichte vol. 41, page 229 and 66, page 1223.

All of the foregoing furoquinoxalines and thiencquinoxalines act as strong accelerating with materials containing,

agents for the dye destruction by dye bleaching These compounds may be employed not only in a non-oxidizing insitu' with metallic silver.

mineral acid bleach bath such as hydrochloric,

hydrobromic, hydriodic, sulfuric, sulfamic or phosphoric acid but also in relatively Weak water soluble organic acids such as acetic, propionic,

tartaric, citric, boric or aryl sulfonic' acid, e. g., benzene, disulfonic or naphthalene ,trisulfonic acid. Their action is further accelerated by the presence of' halide ions which may be added in the form of a halogen acid or in the form of a water soluble halide such as sodium, potassium,"

or ammonium bromide or iodide, ammonium chloride and the like.

The concentration of the mineral acid em'-' ployed is dependent upon'the character of the photographic color emulsion layer or layers used 1 for color film containing azo dyes. The concen tration of the acid may range from 5 to mls. per liter of dye bleach solution but its upper limits are controlled by the resistance of the colloidal carrier to the action of acids. Furthermore, the concentration of acid used for the treatment of photographic film containing developed azomethine and quinonimine dye images must be kept sufiiciently low to avoid their destruction by the action of acid. to 4.0 is preferred.

The furoquinoxalines and thienoquinoxalines are water soluble, only very weakly colored, and do not stain gelatin. The amount employed when used as catalysts is not critical but within practical limits, an increase of concentration will increase the catalytic activity. An amount as small as 0.005 gram per liter of bleach solution will have an appreciable bleaching action on silver bearing images.

rangin from of solubility of the catalyst in the bleach solution may be employed. However, the preferred range I is 0.005 to 1 gram per liter.

A film containing a negative silver image and dyed uniformly with an azo dye will, upon treatment with a dye bleach solution containing a furoquinoxaline or a thiencquinoxaline, be decolorized in those places where silver images are present in proportion to the concentration of the silver. Complete decolorization or dye destruction will take place at points where considerable amounts of silver aredeposited. In the areas where little or no silver is present, little or no dye will be destroyed. The destruction will be partial and will vary with the silver density in intermediate regions. In this manner, the dye image of a character opposite to the silver image is formed. Consequently, if the silver image is negative, a positive dye image is obtained'and vice versa.

It is known that azomet-hine and quinonimine dye images obtained by color forming development are bleached and destroyed by strong mineral acids such as those used in silver dye bleach procedures. F bleach solutions cannot be used in conjunction developed azomethine and quinonimine dye images.

However, since the furoquinoxalines and thienoquinoxalines are non-staining, their concentration in bleach solutions can be increased to such a degree that weak acids such as those listed I above may be used. The pI-I of such a dye bleach bath can be adjusted so that it is no longer so low that it will destroy the azomethine dye or a quinonimine dye image irreversibly. For this rea- The pH range of from 2.0

For practical purposes, amounts. 0.005 gram per liter up to the limit or this reason, conventional dye son, a dyebleach solutionutllizinga) weakhcid instead of a strong acid suchas: hydrochloric acid can be usedfor theformation-eradye mask in a monopack multilayer 1y azomethine and quinoniminedye images had been formed by-dye coupling procedures. The following examples will illustrate the use of dye bleach baths containing furoquinoxalin'es andthienoquinoxalines as catalysts.

Example. I

A red-sensitive; silver halide emulsiomcontaining Dianil Blue. G (Schultz, #5114, .1931: 7th ed;,v Vol.1) was coated. on afilmhase, dried, exposed: through a transparency, white developer, shortstoppediand washed-briefly. Thesfilm strip was then. immersedior. 3 minutes in a bleach solution having. the followingzcompmsition:

Hydrobromic acid (35 ;ml' i120 Benzofuro[2,'3-bl quinoxaline gram .05 v Waterto make 1 liter.

The film was washed for Z'minutes bleached; in a potassium ferricyanide-potassium bromide solution for 3 minutes, washed for 3 minutes, fixed for 5 minutes. and. finally washe'dlfor minutes and dried. An inspection of the driedl film strip showed that the cyan dye/had: been destroyed in proportion to the amount. of. developed silver present. Th highlight'areaswere completely clear, showed complete: removal ofthe dye and did not give any indication otresidualv stain.

EzcampleH developed-inablaclcandi film in whichprev ious- A green-sensitive silver'halide emulsion containin Brilliant Red B (Schultz; #423) was coated on a film base and dried. The film was exposed through a color transparency; developed in a black and white developer, shortstopped'and washed for several minutes. The shortstopped' film was treated for 10 to 12 minutes in a dye bleach bath of the following composition:

Potassium iodide -grams Hydrochloric acid ml 100' 9-methy1benzofuro[2,3.-bl quinoxaline grams- 0.005; Water to make 1 liter.-

The bleached film was washed briefly, bleached in a ferricyanide bromide solution for 5 minutes, washed, fixed and finally washed again. A

magenta image with clear highlights and free fromstain was obtained.

Example. III

A blue-sensitive silver halideemuls'ion contain-- ing diphenyl biguanide-hydrochloride. and Benzo Fast Yellow R. L. (C. 1. #349A) was coated ona film base, dried, exposed: through a transparency, developed in a black and white de-- veloper and shortstopped. The film was treated 4 for 10 to 15 minutes in a dyebleachbath ofthe following composition:

Potassium iodide grams Hydrochloric acid (35%) .ml.. 100.

Benzothieno [2,3 b quinoxaline gram..- 0.05 Water to make 1 liter. 1

Complete bleaching of the yellow 'layertookplace' within 10 minutes with 'theformation'of a yellow dyestufi image.

Example-IV A green-sensitive silver halide emulsion containing diphenyl biguanide hydrochloride and Fast Acid Magenta (C. I. #30) was coated on a glass plate, dried and exposed through a transparency, developed in a black, and white developer, shortstopped and fixed. The fixed film was treated for 10 to 15 minutes in a dye bleach bath of the following composition:

1 Grams Potassium iodide 8 Glacial acetic acid" 75 Naphtho 1, 2, 4,5 thieno[2,3-b1quinoxaline- 0.1 Water to make 1 liter.

A red colored imagewith clear highlights and -'free from stain was formed.

Example V Grams Metol 1.5 Sodium sulfite (anhydrous). 80.0 Hydroquinone 3.0 Potassium bromide. 0.5

Water to make 1 liter.

The developed film was then shortstopped for 3 minutes in a shortstop bath having the following composition:

Sodium acetate grams 20 Acetic acid cc 10 Water to make 1 liter.

It was fixed for 3 minutes in a solution of the following composition:

Hypo grams 240 Sodium sulfite (anhydrous) do 15 Acetic acid (28%) aqueous solution ml 45 Potassium alum grams 15 Water to make 1 liter.

The film was then immersed for 3 minutes in a silver. dye. bleach solution. having the following composition:

Benzofuro[2,3'-b]quinoxaline gram 0.01 'I-lydrobromic acid (35%) ml Water to make 1 liter- The film strip was then washed for 2 minutes, bleached in a ierricyanide solution containing potassium bromide for 3 minutes, washed for 3 minutes, fixed; for 3 minutes. and finally washed for 20 minutes and then dried. A direct positive: reproduction of the original transparency wasthus obtained. Ithad completely clear highlight areas and showed no indication of residual stain.

Example VI A red-sensitivesilver halide emulsion containing l-hydroxy-4-sulfo-N-stearyl-2-naphthamide as a color former for the. cyan image is dyedwith Brilliant Purpurine 10B (Schultz "1th Ed.

#423) and diphenyl biguanide hydrochloride is added as aprecipitating agent forsaid dye. The

emulsion is coated on a film base producing a dye emulsion thickness of approximately 7 microns and having a dye density of 1.0 at maximum absorption.

A green-sensitive silver'halide emulsion layer containing 1 (4 phenoxyphenyl 3' sulfonic acid) -3-stearyl-5-pyrazolone as a color former for the magenta image, Benzo Fast Yellow (C. I.

1st Ed. #349A) as an azo masking dye, and diphenyl biguanide hydrochloride as a precipitating agent for the azo dye is coated on top of the cyan layer. After drying, this layer has a density of 1.5 at maximum absorption.

Over the magenta layer is coated a yellow filter followed by a blue-sensitive silver halide emulsion layer containing 5-(4-stearylaminobenzoylacetamino)terephthalic acid as a nondifiusing color former for the yellow dye image.

After exposure, the film is color developed for approximately minutes at 68 F. in the following color developer:

Grams p-Di (fi-hydroxyethyl) aminoaniline 6 Sodium hexametaphosphate 1 Sodium bisulfite 2 Sodium carbonate (monohydrate) 100 Hydroxylamine hydrochloride 1 Potassium bromide 1 Water to make 1 liter.

At this stage, the film contains negative dye and silver images in the top layer, negative magenta plus silver images and a uniform yellow azo dye in the magenta layer, and negative cyan plus silver images and a uniform reddish azo dye in the cyan layer. The film is washed, shortstopped and subjected to the action of a dye bleach bath having the following composition:

Grams Potassium iodide 90 Acetic acid 90 Benzofuro[2,3-blquinoxaline 0.4

Water to make 1 liter.

In this bath, the yellow and reddish azo dyes in the middle and bottom layers respectively are destroyed in situ with the negative silver images in these layers leaving a magenta negative dye printing image and a positive yellow masking image in the middle layer, and a cyan negative dye printing image and a reddish positive masking image in the bottom layer. The top layer contains a yellow negative dye printing image besides the silver.

The length of time the film is treated in the bleach bath is determined by the time required to bleach the azo dyes and generally will not be sufiicient to convert all of the silver into silver salts. Therefore, a treatment with an oxidizing silver bleach bath such as a ferricyanide or copper chloride solution which may contain bromide ions is used to convert the residual silver in all layers to a silver salt soluble in hypo. Following the latter bleaching treatment, the film is fixed and washed in the usual manner.

Example VII materials and uses, it is understood that the invention is not limited thereto, that numerous variations may be made in the procedure described herein, and that equivalent materials may be substituted. Thus, for example, other color formers and other primary aromatic amino color developing agents may be used. Similarly, azo dyes other than those specifically mentioned and utilized in the foregoing examples may be bleached satisfactorily. Several hundred such dyes are known and further reference to them or to their methods of preparation need 'not be made herein. In the examples, any of the generally employed processing solutions (excluding the silver dye bleach bath) may be used. Finally, it is apparent that any of the furoquinoxalines or thienoquinoxalines listed above may be used to replace those of the examples.

I claim:

1. A silver dye bleach bath comprising an aqueous solution of a water soluble halide and an acid selected from the class consisting of nonoxidizing mineral acids and water soluble organic acids and an accelerator of the general formula:

N U A/\N/ wherein A is an atom selected from the group consisting of oxygen and sulfur and Z and Z represent the atoms necessary to complete a carbocyclic ring system of the benzene, naphthalene, anthracene and acenaphthene series.

2. A dye bleach bath according to claim 1 in which the accelerator is benzofuro[2,3-blquinoxaline.

3. A dye bleach bath according to claim 1 in which the accelerator is Q-methylbenzofuro [2,3-blquinoxaline.

4. A dye bleach bath according to claim 1 in which the accelerator is 1,3-dimethylbenzofuro [2,3-b] quinoxaline.

5. A dye bleach bath according to claim 1 in which the accelerator is naphtho[l',2',4,5lthieno- [2,3 -b quinoxaline.

6. A dye bleach bath according to claim 1 in which the accelerator is benzothieno [2,3-b] quinoxaline.

7. A silver dye bleach bath comprising an aqueous solution of acetic acid, a halide capable of forming a silver salt of low solubility, and as an accelerator, benzofuro[2,3-b1quinoxaline.

8. A silver dye bleach bath comprising an aqueous solution of acetic acid, a halide capable of forming a silver salt of low solubility and as an accelerator, benzothieno [2,3-b] quinoxaline.

9. The process of producing a colored image in a photographic layer containing a silver image and a bleachable azo dye which comprises destroying the dye in situ with said image by bleaching said layer in a bath comprising an aqueous solution of an acid selected from the group consisting of non-oxidizing mineral and water soluble organic acids, a water soluble halide and a compound of the general formula:

wherein A is an atom selected from the group consisting of oxygen and sulfur and Z and Z' represent the atoms necessary to complete a car- 11 bocyclic ring system of the benzene, naphthalene, anthracene and acenaphthene series.

10. The process according to claim 9 in which the accelerator is benzofuro[2,3-b]quinoxaline.

11. The processaccording to claim 9 in which the accelerator is 9-methylbenzofuro[2,3-b]quinoxaline.

12. The process according to claim 9 in which the accelerator is 1,3-dimethylbenzofuroL2,3 b quinoxaline.

13. The process according to claim 9 in which the accelerator is naphtho[1,2,4,51thieno[2,3- blquinoxaline.

14. The process according to claim 9 in which the accelerator is benzothieno[2,3-b]quinoxaline.

15. The processof producing a colored image in a photographic layer containing a silver image .ing said layer in a and a bleachable azo .dye which comprises destraying said dye at said silver image by bleachbath comprising an aqueous solution of acetic acid, a water soluble halide, and. as an accelerator, benzofuro[2,3-blquinoxaline.

16. The process of producing a colored image in-a-vphotographiolayer containing alsilver image and a bleachable azo dye which comprises vtie-- stroying said dye atsaid image by bleaching said layer in a bath comprising .an aqueous solution of acetic acid,.a water solublethalide, and aneccelerating amount of benzothienoc[2,3-blquinoxaline.

FRITZ W.,H.

No references cited. 

1. A SILVER DYE BLEACH BATH COMPRISING AN AQUEOUS SOLUTION OF WATER SOLUBLE HALIDE AND AN ACID SELECTED FROM THE CLASS CONSISTING OF NONOXIDIZING MINERAL ACIDS AND WATER SOLUBLE ORGANIC ACIDS AND AN ACCELERATOR OF THE GENERAL FORMULA: 